You may have noticed that Tom Cruise and Katie Holmes are getting divorced. Their marital liquidation was preceded by news of another: Dominique Strauss Kahn, former head of the IMF and former defendant in a sexual assault case, was reportedly being left by his hitherto supernaturally loyal wife, Anne Sinclair.

The two men have something in common; or rather, the two departing women have something in common: they’re both third wives.

While Holmes’ divorce filing apparently blindsided Mr Cruise, who was away on location filming a movie, neither split was all that unexpected. It’s not just because celebrity magazines have been predicting a TomKat rupture since the day their wedding vows were uttered, or that, you know, Mr. Strauss Kahn was a cheat. It’s because third marriages break up more often than first or second unions.

There’s a figure floating around the Internet that some 70% of third marriages fail, but the real numbers tell a slightly different story. It’s also commonly agreed that about half of all marriages fall apart, but while true, that stat also doesn’t tell the full story.

Overall, divorce rates are actually falling. And among the well-educated and wealthy who marry after the age of 26, they’re falling quite dramatically. The vast majority of American marriages between two people like Cruise and Holmes make it to the 10-year mark. (Theirs lasted six.) About 30% of people in Cruise’s demographic — white American men between the ages of 40 and 49 (Cruise’s age when Holmes filed for divorce) — have ever been divorced, according to the most recent (2009) Census figures. And half of them had remarried. About 12% of those guys had then divorced again. That is, 24% of fortysomething white guys’ second marriages had failed.

Which brings us to third marriages, after which point the Census stops counting. It feels like a lot of people are in — or leaving — their third marriage (hello, Kelsey Grammer!), but they aren’t. Cruise’s case is quite unusual (even apart from his weird superstar-stinking-rich-Scientologist combo). Only about 3.4% of Cruise’s age-race cohort have been married three times or more, according to the Census. And about 0.9% of them were divorced. So, although not many white guys in their 40s have married three times or more, more than a quarter of the ones who have, get divorced again.

This may be grim news for the next Mrs. Cruise. For Ms. Holmes, however, the outlook is somewhat rosier: only 17% of women in Katie’s cohort, white women between the ages of 30 and 34 have ever been divorced. Nine percent of her ilk have been married twice. And almost 8% of women that age are still married to their second spouses. So about 90% of those marriages are surviving. She’s young, she’s professionally successful, she’s wealthy, she’s got a very cute kid. The numbers are on her side.

Suri may be the one we have to watch out for. Kids whose parents cycle in and out of too many relationships have a higher chance of getting divorced themselves; they also have a lower chance of getting through college and face a whole bunch of other unfortunate life outcomes. Some of this, though, is connected to poverty. If all of the fine legal minds that will be pressed into service on the Cruise-Holmes divorce case do their job responsibly, Suri shouldn’t have to worry about that.